A remarkable feature of smart biomaterials is their ability to deform in response to certain external bio-stimuli. Here, a novel biochemo-electro-mechanical model is presented for theoretical characterization of urea-sensitive hydrogel in response to external stimulus of urea, by the states of ionization and denaturation of the immobilized urease, where the model includes the effect of the fixed charge groups and temperature coupled with pH on the activity of the urease. Here, a novel rate of reaction is proposed to characterize the hydrolysis of urea that accounts for both the ionization and denaturation states of the urease subject to environmental conditions. After examination with published experimental data, it is confirmed that the model can characterize well the responsive behavior of the urea-sensitive hydrogel subject to the urea stimulus, including the distribution patterns of the electrical potential and pH within the hydrogel. The results point to the innovative means for generating electrical power via the enzyme-induced pH and electrical potential gradients, when the hydrogel contacts with the urea-rich solution, such as human urine.

The recent surge in the number of studies on seismic metamaterials is testimony to the fact that the concept of photonic crystals, phononic crystals and acoustic metamaterials is no longer limited to basic theories and dynamic characteristics. Apart from the peculiar observation including negative stiffness, negative mass density negative refraction properties, etc., auxetic metamaterials that govern negative Poisson’s ratio, nonreciprocal wave phenomena, origami/kirigami effects also find potential applications in geophysics and earthquake engineering. Except man-made synthetic resonators/metastructures, recently forest trees at geophysical scale are reported as naturally available seismic metamaterials with capability to mitigate ground born ambient vibrations and incoming seismic waves at subwavelength frequency region. The work to be presented here elaborates a class of materials and structures ranging from engineered phononic crystals and acoustic metamaterials to natural seismic metamaterials that show exotic yet with outstanding application potentials. Besides discussing the peculiar yet wonderful wave propagation characteristics of periodic structures for wave active control, topological protected interface modes, etc., the exciting wave dispersion response that found applications for manipulation Rayleigh wave and possible forestation as a means for geographical regional isolation against ground surface wave motion will also be presented.

Over the past few decades, there has been remarkable progress in the development of low-powered smart wireless sensors and portable devices. However, a major challenge lies in providing continuous power sources for these sensors and devices. Meanwhile, there are a lot of complex environmental vibrations induced by mechanical equipment, vehicles, wind, ocean waves, etc. Small-scale mechanical energy harvesting which can be considered as new green energy has great potential to solve above challenging issue. How to design, model and test high-performance mechanical energy harvesters is of great interest. Based on recent research progress of his group, this presentation will discuss the design, modeling, dynamic analysis and experimental tests of small-scale mechanical energy harvesters subjected to different kinds of excitations, such as broadband base and rotational excitations, and time-varying wind speeds.